Cellar mobile phones provide an extremely great convenience to communication of the people. The 2nd generation global mobile communication system (GMS: Global System for Mobile Communication) provides further improvement of communication quality in mobile communication by adopting digital communication techniques. The 3rd generation partnership project (3GPP) as an important organization in the mobile communication field has extensively promoted standardization of the generation mobile communication technology (3G: The Third Generation) and established a series of communication system standards such as WCDMA (Wide Code Division Multiple Access), HSDPA (High Speed Downlink Packed Access) and HSUPA (High Speed Uplink Packet Access).
In order to address challenges of the wideband access technique and respond to growing demand for new services, the 3GPP has started standardization of the 3G long-term evolution (LTE) since the end of 2004. This is planning to improve spectrum efficiency and performance of cell-edge users, reduce system delay and provide a higher-speed access service to high-speed mobile users. The LTE-A technology provides high-speed and excellent-performance services to more mobile users by multiplying data rate and increasing the frequency bandwidth by several times based on the LTE technology.
In the LTE-A system, a multi-user Multiple-Input Multiple-Output (MU-MIMO) technique is supported. That is, in the LTE-A system, a plurality of user apparatuses (UE) can be scheduled simultaneously in same-frequency resources. In other words, in the LTE-A system, plural UE apparatuses can share frequency resources such as resource blocks. The UE apparatuses sharing same frequency resources can be called a coordinated transmission group participating in the MU-MIMO transmission. As to the UE apparatuses, they can be classified by transparency under two, a transparent UE group and a non-transparent UE group. The transparent UE means a UE apparatus that can only know its own data demodulation information (for example, a demodulation reference signal (DM-RS) port, the number of data streams of RBs assigned to itself (Rank), and so on) and cannot know whether or not there exists another UE apparatus in the present coordinated transmission group. In other words, the transparent UE apparatus does not know whether it is a single user Multiple-Input Multiple-Output (SU-MIMO) user or a MU-MIMO user. The MU-MIMO technique based on this condition is called “transparent MU-MIMO technique”. The non-transparent UE is a UE apparatus that can recognize not only its own data demodulation information but also demodulation information of other UE apparatuses in the present coordinated transmission group (for example, DM-RS ports, Ranks of RBs assigned to UE apparatuses in the coordinated transmission group and so on). That is, the non-transparent UE apparatus can know that it is a SU-MIMO user or MU-MIMO user. In the LTE-A standardization process, Release 10 (Rel-10), the LTE-A system is defined as needing to support the transparent MU-MIMO technique.
In the LTE-A system (abbreviated as “MU-MIMO system”) supporting the transparent MU-MIMO technique, the UE apparatus suffers from inter-cell interference (ICI) from neighbor cells and also from multi-user interference (MUI) from other users in the coordinated transmission group. As the transparent UE apparatus cannot know demodulation information of other users in the coordinated transmission group, it cannot remove MUI. For example, when an advanced receiving apparatus such as an IRC (interference Rejection Combining) receiving apparatus is used, it is possible to bring about significant gains, while suppressing interference. However, in the conventional method, as the transparent UE apparatus cannot know demodulation information of other users in the present coordinated transmission group, it cannot perform accurate interference rejection of MUI, even using the IRC receiving apparatus.
FIG. 1 illustrates an inner structure of a conventional IRC receiving apparatus. As illustrated in FIG. 1, the conventional IRC receiving apparatus has a demodulation information obtaining section 101 configured to extract demodulation information of the own station such as a DM-RS port identifier (ID), a DM-RS scrambling sequence index (SCID) and the like from physical downlink control channels (PDCCHs) of reception signals, a first channel estimating section 102 configured to perform channel estimation on downlink data channels of the own station based on the demodulation information of the own station, a second channel estimating section 103 configured to perform channel estimation on MUI signals in the reception signals, a third channel estimating section 104 configured to perform channel estimation on ICI signals in the reception signals, a reception coefficient generating section 105 configured to generate a reception coefficient based on channel estimation results of the first channel estimating section 102, the second channel estimating section 103 and the third channel estimating section 104, and a data detecting section 106 configured to perform data detection on transmission data in physical downlink shared channels (PDSCHs) of the reception signals based on the generated reception coefficient and obtain data transmitted from the base station to the own station.
In order to perform cell selection, handover and other operations, the above-mentioned IRC receiving apparatus has to have another module to measure reference signal reception power (RSRP) and reference signal reception quality (RSRQ) of reception signals.